Trailer vehicles that have a brake system, a light system and a control device for controlling the light system are known. The brake system has the function of controlling the braking behavior of the trailer vehicle. The light system comprises various light elements, for example brake lights, reversing lights, turn signals or side marker lights. The status of the light system can be changed by means of the control device, for example a brake light, a reversing light, a turn signal, a warning light and/or a side marker light can be activated or deactivated.